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#c++ #dsa #linkedlist #reverselinkedlist #recursion #circular

// check if a linked list is circular or not
bool isCircular (node* head) {
  if (head == NULL) {
    return true;
  }
  node* temp = head -> next;
  while (temp != NULL && temp != head) {
    temp = temp -> next;
  }
  if (temp == head) {
    return true;
  }
  return false;
}

#c++ #dsa #linkedlist #reverselinkedlist #recursion

code to reverse a linked list in the group of k

node* kReverse (node* head, int k) {
  // base case
  if (head == NULL) {
    return NULL;
  }

  // step 1: reverse first k nodes
  node* forward = NULL;
  node* curr = head;
  node* prev = NULL;
  int cnt = 0;
  while (curr != NULL && cnt < k) {
    forward = curr -> next;
    curr -> next = prev;
    prev = curr;
    curr = forward;
    cnt++;
    
  }
  // step 2: recursion
  if (forward != NULL) {
    head -> next = kReverse(forward, k);
    
  }
  // step 3: return head of the modified list
  return prev;
}

#c++ #dsa #linkedlist #reverselinkedlist #recursion #middlenode

return the middle node in linked list and in the case of two node return the further one from head

int getLength (node* head) {
  int length = 0;
  node* temp = head;
  while (temp != NULL) {
    length++;
    temp = temp -> next;
  }
  return length;
}

node* middleNode (node* head) {
  int length = getLength(head);
  int mid = (length/2) + 1;
  int cnt = 1;
  node* temp = head;
  while (cnt < mid) {
    temp = temp -> next;
    cnt++;
  }
  return temp;
}

#c++ #dsa #linkedlist #reverselinkedlist #recursion

reverse linked list using recrsion

node* reverseLinkedList (node* & head) {
  //empty list or single node
  if (head == NULL || head -> next == NULL) {
    return head;
  }
  node* prev = NULL;
  node* curr = head;
  node* forword = NULL;
  while (curr != NULL) {
    forword = curr -> next;
    curr -> next = prev;
    prev = curr;
    curr = forword;
  }
  return prev;
}

#c++ #dsa #linkedlist #reverselinkedlist #recursion

reverse linked list using recursion

// it will return the head of the reversed linked list
node* reverse1 (node* head) {
  // base case
  if (head == NULL || head -> next == NULL) {
    return head;
  }
  node* chotaHead = reverse1(head -> next) {
    head -> next -> next = head;
    head -> next = NULL;

    return chotaHead;
  }
}

#c++ #dsa #linkedlist #reverselinkedlist

reverse linked list

node* reverseLinkedList (node* head) {
  // empty  list 
	if (head == NULL || head -> next == NULL) {
	return head;
	}
  node* prev = NULL;
  node* curr = head;
  node* forword = NULL;
  
  while (curr != NULL) {
	forword = curr -> next;
    curr -> next = prev;
    prev = curr;
    curr = forword;
  }
  return prev;
}

check if linked list is circular or not

code to reverse a linked list in the group of k

return the middle node in linked list and in the case of two node return the further one from head

reverse linked list using recrsion

reverse linked list using recursion

reverse linked list

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